The libevent ... appeared to run fine.
The first sfs delta I tried generated this:
I tried creating a folder "orig" and putting a copy of the sfs in there with the delta.xdelta3: using default output filename: /mnt/home/jl64-603g/orig/JL64-603g.sfs
xdelta3: using default source filename: /mnt/home/jl64-603g/orig/JL64-603g.sfs
xdelta3: source /mnt/home/jl64-603g/orig/JL64-603g.sfs winsize 64 MB size 281604096
xdelta3: to overwrite output file specify -f: /mnt/home/jl64-603g/orig/JL64-603g.sfs
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It's still unclear to me how this is supposed to work.
Why doesn't it just create a second updated version of the sfs right where it is, with a slightly different name, then the user can manually swap the new for the old?